1. Field of the Invention
The present invention relates to a method and system for mobile number portability (MNP) service in an asynchronous mobile communication network and, in particular, to a method and system of which performance is improved by storing whether mobile subscriber changed his mobile service provider and an address of a Number Portability Database (NPDB) in a service network where the mobile subscriber gets to subscribe and by performing mobile number portability inquiry, in the NPDB using the address, only for a mobile subscriber who practically changed his mobile service provider.
2. Description of the Related Art
Generally, the MNP service supports mobile subscribers to change mobile service provider without changing their mobile station number (Hereinafter, “mobile number”) and is specifically described in 3rd Generation Partnership Project (3GPP) Technical Specifications (TS) 23.066 Support of MNP Technical Realization Phase 2.
When a mobile service provider provides a mobile subscriber with mobile service at first, the mobile service provider provides the mobile subscriber with Mobile Subscriber Identification Number (MSIN) and Mobile Station Integrated Service Digital Network (ISDN) Number (MSISDN).
The MSIN is a number for identifying mobile subscribers, used by a mobile service provider, and the MSISDN is a mobile number of a mobile subscriber.
If a mobile subscriber wants to change his mobile service provider, the mobile subscriber should abandon the MSISDN given by a previous mobile service provider and receive a new MSISDN from a new mobile service provider.
To change MSISDN is too complicated and causes uncomfortable-ness that a mobile subscriber informs people, who know the previous MSISDN, of the new MSISDN again.
Accordingly, it is comfortable that a mobile subscriber is able to use a previous MSISDN in spite of change of a mobile service provider.
The MNP service enables mobile subscribers to use same MSISDN in spite of change of mobile service provider and there are Terminating call Query on Digit analysis (TQoD) method and Query on HLR Release (QoHR) method in systems providing the MNP service.
First, MNP service network according to the TQoD method, as illustrated in attached FIG. 1, includes: an originating network 10 attempting calls; a previous service network 20 terminating calls until a mobile subscriber changed his mobile service provider; and a current service network 30 where the mobile subscriber presently subscribes. The previous network 20 includes, as components for providing the MNP service: a Gateway Mobile Switching Center (GMSC) 21 that processes call processing between networks; and an NPDB 22 where information of the mobile subscriber, who changed his mobile service provider, is stored.
Nodes are connected through intelligent network protocol messages. ITU-T SS7 ISUP protocol is used between the originating network 10 and the GMSC 21 or between the GMSC 21 and the current service network 30. 3GPP Customer Application for Mobile Network Enhanced Logic (CAMEL) protocol is used between the GMSC 21 and the NPDB 22, for controlling details and processing messages.
Second, MNP service network according to the QoHR method, as illustrated in attached FIG. 2, includes: an originating network 10 attempting calls; a previous service network 20 terminating calls until a mobile subscriber changed his mobile service provider; and a current service network where the mobile subscriber presently subscribes. The previous network 20 includes, as components for providing the MNP service: a GMSC 21 that processes call processing between networks; an NPDB 22 where information of the mobile subscriber, who changed his mobile service provider, is stored; an HLR 23 where location or general information of the mobile subscriber is stored.
ITU-T SS7 ISUP (ISDN User Part) protocol is used for connecting the originating network 10 and the GMSC 21 or connecting the GMSC 21 and the current service network 30. 3GPP Mobile Application Part (MAP) protocol is used for connecting the GMSC 21 and the HLR 23. 3GPP CAMEL protocol is used for controlling details and processing messages between the GMSC 21 and the NPDB 22.
The NPDB, one of components making up the MNP service network, includes an MNP service logic supporting multiple protocols; and an MNP routing table corresponding to each MNP service logic. When an inquiry message is inputted from the GMSC, the NPDB analyzes a protocol applied to the inquiry message and, then, pages MNP service logic corresponding to the protocol. The MNP service logic obtains routing information about called subscriber from the MNP routing table by using mobile number of the called subscriber as service key.
Then, the NPDB transfers the obtained routing information to the GMSC, using the same protocol as the protocol used for the inquiry message.
Hereinafter, the MNP service in the above-mentioned network will be described in detail with reference to attached drawings. First, in the MNP service according to the TQoD method, as illustrated in FIG. 3, call originated from the originating network 10 transfers an MSISDN of a called subscriber to the GMSC 21 in the previous service network 20, with loading the MSISDN of the called subscriber on an ISUP_Initial Address Message (IAM) according to ITU-T SS7 ISUP protocol (S301), since it is determined that the mobile subscriber still uses previous mobile number as a result of translating mobile number.
Then, the GMSC 21 transfers the MSISDN of the called subscriber to the NPDB 22, with loading the MSISDN, received from the originating network 10, on the CAMEL_Initial Detection Point (IDP) message according to 3GPP CAMEL protocol, in order to request mobile number portability inquiry (S302).
If a mobile subscriber subscribes to another service network and mobile number of the mobile subscriber is changed, the NPDB 22 transfers a routing number of the mobile subscriber, an actual called number given to the called subscriber by the current service network 30, to the GMSC 21, with loading the routing number on CAMEL_CONNECT message according to 3GPP CAMEL protocol (S303).
The GMSC 21 translates the routing number loaded on the received CAMEL_CONNECT message and, then, transfers the routing number to the current service network 30, with loading the routing number on ISUP_IAM according to ITU-T SS7 ISUP protocol (S304). Then, a call is connected to the called subscriber in the current service network 30 according to a mobile call processing procedure.
Second, as illustrated in FIG. 4, in the MNP service according to the QoHR method, a call originated from the originating network 10 transfers an MSISDN of a called subscriber to the GMSC 21 in the previous service network 20 for call connection request, with loading the MSISDN on ISUP_IAM according to ITU-T SS7 ISUP protocol (S401), since it is determined that the mobile subscriber still uses a previous mobile number as a result of translating mobile number.
The GMSC 21 transfers the MSISDN to the HLR 23, in order to inquire about called subscriber information, with loading the MSISDN on MAP_Send Routing Information (SRI) message, which is mobile subscriber information inquiry request message according to 3GPP MAP protocol.
However, the HLR 23, which does not have the subscriber information due to the mobile subscriber's change of mobile service provider, transfers 3GPP MAP_SRI_Negative Response (NRP) message, information inquiry failure response message according to 3GPP MAP protocol, with ‘INVALID SUBSCRIBER’ sign to the GMSC (21) (S403).
The GMSC 21 which received the MAP_SRI_NRP message, in order to inquire about mobile number portability of the called subscriber, transfers the MSISDN to the NPDB 22 in the previous service network 20, with loading the MSISDN on the CAMEL_IDP message, mobile number portability request message according to 3GPP CAMEL protocol (S404).
The NPDB 22 transfers a routing number of the mobile subscriber, an actual called number given to the called subscriber by the current service network 30, to the GMSC 21 by loading the routing number on the CAMEL_CONNECT message according to 3GPP CAMEL protocol (S405).
The GMSC 21 translates the routing number loaded on the received CAMEL_CONNECT message and, then, transfers the routing number to the current service network 30 by loading the routing number on the ISUP_IAM according to ITU-T SS7 ISUP protocol (S406). Then, the call is connected to the called subscriber in the current service network 30 according to a mobile call processing procedure.
The MNP service of the related art has a problem in that NPDB server corresponding to the number of service networks has to be provided in every service network cooperating with one current service network for MNP service.
More specifically, one routing number management server allotting a routing number and N-1 mobile number portability inquiry server inquiring about mobile number portability of a called subscriber, have to be provided in each N service network.
According to the MNP service of TQoD method, mobile number portability inquiry about all mobile subscribers is performed in the NPDB, so that even a call for a mobile subscriber who does not change his mobile service provider has to go through the mobile number portability inquiry in the NPDB, thereby declining system performance.
According to the MNP service of QoHR method, it has an advantage in that system performance is improved, compared with TQoD method, because mobile number portability inquiry in an NPDB is performed only for a mobile subscriber, whose location information inquiry is failed. However, it still has a problem in system performance because mobile number portability inquiry in an NPDB is performed for all cases where the location information inquiry is failed and the called subscriber is determined as ‘INVALID SUBSCRIBER’.